Battery module of high cooling efficiency

ABSTRACT

Disclosed herein is a battery module including a plurality of unit cells stacked one on another. The battery module has a cooling system that accomplishes contact type cooling by a coolant flowing through gaps (flow channels) defined between the unit cells, and the flow channels defined between the unit cells are at a predetermined angle to the flowing direction of the coolant at inlet ports of the flow channels. The contact rate of the coolant to the unit cells in the battery module is increased and a large number of turbulent flows are created by the changing the flow channel through which the coolant flows. Consequently, the occurrence of the velocity gradient of the coolant in the flow channel defined between the unit cells is prevented, and therefore, the cooling efficiency of the battery module is improved.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 11/560,512, filed on Nov. 16, 2006, the contents of which areincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a battery module having high coolingefficiency, and, more particularly, to a battery module having a coolingsystem for cooling a plurality of unit cells by a coolant flowingbetween the unit cells, wherein flow channels, through which the coolantflows between the unit cells, are at a predetermined angle to an inletports of the flow channels, whereby the contact rate of the coolant tothe surfaces of the unit cells is increased, the turbulent flowgenerating rate in the coolant flow channels is increased, andtherefore, the battery module has high cooling efficiency under the sameconditions.

BACKGROUND OF THE INVENTION

One of the biggest problems caused from vehicles using fossil fuel, suchas gasoline and diesel oil, is creation of air pollution. A technologyof using a secondary battery, which can be charged and discharged, as apower source for vehicles has attracted considerable attention as onemethod of solving the above-mentioned problem. As a result, electricvehicles (EV), which are operated using only a battery, and hybridelectric vehicles (HEV), which jointly use a battery and a conventionalengine, have been developed. Some of the electric vehicles and thehybrid electric vehicles are now being commercially used. A nickel-metalhydride (Ni-MH) secondary battery has been mainly used as the powersource for the electric vehicles (EV) and the hybrid electric vehicles(HEV). In recent years, however, the use of a lithium-ion secondarybattery has been attempted.

High output and large capacity are needed for such a secondary batteryto be used as the power source for the electric vehicles (EV) and thehybrid electric vehicles (HEV). For this reason, a plurality ofsmall-sized secondary batteries (unit cells) are connected in series orin parallel with each other so as to construct a medium- or large-sizedbattery pack.

However, a large amount of heat is generated from the medium- orlarge-sized battery pack during the charge and the discharge of thebattery pack. Most of the heat is generated from the secondarybatteries, which are the unit cells of the medium- or large-sizedbattery pack. When the heat generated from the unit cells during thecharge and the discharge of the battery pack is not effectively removed,heat is accumulated in the battery pack with the result that the unitcells are degraded. According to circumstances, the unit cells may catchfire or explode. Consequently, it is necessary to provide a coolingsystem for preventing the catching fire or explosion of the unit cells.

The cooling system is constructed in a structure in which a coolant isforcibly circulated through the interior of the battery pack so as toremove heat from the unit cells, i.e., in a contact type coolingstructure in which the coolant is brought into contact with the surfacesof the unit cells constituting the battery pack. Air is mainly used asthe coolant. Consequently, the cooling system is generally constructedin a contact type air cooling structure.

Meanwhile, prismatic batteries or pouch-shaped batteries, which can bestacked one on another to reduce the size of a dead space, are used asthe unit cells. In order to easily accomplish the mechanical couplingand the electrical connection between the unit cells, a cartridge, inwhich one or more unit cells are mounted, is used. And a plurality ofcartridges, in which the unit cells are mounted, are stacked one onanother so construct a battery pack.

The cartridge may have various shapes. In addition, the cartridge may beconstructed in a structure in which the unit cells are fixed to a framemember while most of the outer surfaces of the unit cells are open. Anexample of such a cartridge is disclosed in Korean Patent ApplicationNo. 2004-111699, which has been filed in the name of the applicant ofthe present patent application. FIG. 1 illustrates the cartridgedisclosed in the above-mentioned application.

Referring first to FIG. 1, a cartridge 100 comprises a pair of framemembers 120 and 122, which are coupled with each other. Unit cells 200and 201 are located in cell partitions 130 of the frame members 120 and122 while the frame members 120 and 122 are separated from each other,and are then securely fixed at the cell partitions 130 of the framemembers 120 and 122 after the frame members 120 and 122 are coupled witheach other. The unit cell 200 has an electrode lead (not shown), whichis electrically connected to that of the neighboring unit cell 201 via abus bar 140 located at the upper part of the cartridge 100. As shown inFIG. 1, the unit cells 200 and 201 are connected in series with eachother. According to circumstances, however, the unit cells may beconnected in parallel with each other. The unit cells are electricallyconnected to a cathode terminal 150 and an anode terminal 160, whichprotrude from opposite sides of the upper end of the cartridge 100,respectively.

FIG. 2 is a perspective view illustrating a battery module constructedby stacking a plurality of battery cartridges one on another in analternating orientation structure.

Referring to FIG. 2, a plurality of cartridges 101, 102, 103 . . . arestacked one on another in the thickness direction so as to construct abattery module 300. To easily accomplish the electrical connectionbetween the terminals of the cartridges, the second cartridge 102 isstacked on the first cartridge 101 while the second cartridge 102 isoriented in the direction opposite to the orientation direction of thefirst cartridge 101. Specifically, the first cartridge 101 and thesecond cartridge 102 are arranged such that a cathode terminal 152 andan anode terminal 162 of the second cartridge 102 are opposite to acathode terminal 151 and an anode terminal 161 of the first cartridge101. Similarly, the second cartridge 102 and the third cartridge 103 arearranged such that a cathode terminal 153 and an anode terminal 163 ofthe third cartridge 103 are opposite to the cathode terminal 152 and theanode terminal 162 of the second cartridge 102. That is to say, thethird cartridge 103 is arranged in the same orientation as the firstcartridge 101.

As shown in FIG. 1, the height of an upper end frame 110 and a lower endframe 112 of the cartridge 100 is less than that of side frames 11 ofthe cartridge. Consequently, when the cartridges 101, 102, 103 . . . arestacked one on another as shown in FIG. 2, flow channels 170, 171, 172,and 173 are formed in spaces defined between the upper ends of thecartridges 101, 102, 103 . . . and the lower ends of the neighboringcartridges. As a result, a coolant flows in the direction indicated byan arrow.

FIG. 3 is a typical view illustrating the flow of a coolant through theflow channel defined between the battery cartridges of the batterymodule shown in FIG. 2, and FIG. 4 is an enlarged view illustrating partA of FIG. 3.

Referring to FIG. 3, the flow channel 170, which was described abovewith reference to FIG. 2, is formed between the first cartridge 101 andthe second cartridge 102. The respective cartridges 101 and 102 areconstructed in a frame structure in which the outer surfaces of the unitcells are almost fully exposed as shown in FIG. 1. As a result, thecoolant flowing through the flow channel 170 is brought into directcontact with the outer surfaces of the unit cells (not shown).Consequently, the coolant takes heat generated from the unit cells,while the coolant flows through the flow channel 170, and thendischarges the heat out of the battery module.

As shown in FIG. 4, however, when viewing from a microscopic viewpoint,the coolant flowing through the flow channel 170 has a velocity gradientin the hydrodynamic aspect. Specifically, the flow velocity of thecoolant flowing through the flow channel while being near to the surfaceof the unit cell 200 is less than that of the coolant flowing throughthe flow channel while being spaced apart from the surface of the unitcell 200. This velocity gradient is a factor that greatly reduces theefficiency when heat is removed from the outer surface of the unit cell200, i.e., the heat removing efficiency.

Consequently, the necessity of a technology for improving the coolingefficiency by solving the velocity gradient is very high inconsideration of the fact that the coolant-circulating cooling system isprincipally based on a contact type cooling reaction mechanism.

One of methods of improving the cooling efficiency may be a method ofincreasing the flow speed of the coolant to increase the flow rate ofthe coolant adjacent to the unit cells per hour. However, this method isnot preferable in that larger cooling fan or stronger fan driving unitis necessary.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made to solve theabove-mentioned problems, and other technical problems that have yet tobe resolved.

Specifically, it is an object of the present invention to provide abattery module using a coolant contact type cooling system in which thecontact rate of a coolant to the surfaces of unit cells is increased,and the turbulent flow generating rate in coolant flow channels isincreased, whereby the battery module has the high cooling efficiencyunder the same conditions.

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a battery moduleincluding a plurality of unit cells stacked one on another, wherein thebattery module has a cooling system that accomplishes contact typecooling by a coolant flowing through gaps (flow channels) definedbetween the unit cells, and the flow channels defined between the unitcells are at a predetermined angle to the flowing direction of thecoolant at inlet ports of the flow channels.

In the contact type cooling system according to the present invention,as previously described, the coolant takes heat generated from the unitcells while the coolant flows through the flow channels defined betweenthe unit cells. The coolant flow channels are decided based on in whatshape the unit cells are spaced apart from each other. According to thepresent invention, the flow channels defined between the unit cells areat a predetermined angle to the flowing direction of the coolant atinlet ports of the flow channels. Consequently, after the coolant isintroduced through the flow channel inlet ports, and the flow directionof the coolant is inclined while the coolant flows along the flowchannels defined between the unit cells. At this time, turbulent flowsoccur, and therefore, the sectional velocity gradient is prevented. As aresult, the contact rate of the coolant to the unit cells is increased,and therefore, the cooling efficiency of the battery module is improved.

The predetermined angle may be changed depending upon the flow speed ofthe coolant, the size of the gaps defined between the unit cells, ordesired cooling degree. The predetermined angle may be, preferably,between 2 and 30 degrees, more preferably, between 3 and 15 degrees.When the inclination angle is too small, it is difficult to accomplishdesired effects. When the inclination angle is too large, on the otherhand, the flow resistance is increased, and therefore, the flow speed ofthe coolant is greatly decreased, which is not preferable.

The coolant is not particularly restricted so long as the coolant is afluid that can flow through the flow channels and can remove heat fromthe unit cells. Preferably, the coolant is air.

A driving unit used to flow the coolant may be changed depending uponkinds of coolant. In the case that the coolant is the air, the drivingunit may be preferably a cooling fan driven by a motor.

The term used in the specification “battery module” inclusively meansthe structure of a battery system constructed by mechanically couplingand, at the same time, electrically connecting two or more unit cells soas to provide high-output and large-capacity power. Specifically, thebattery module may construct either the entirety of a device or a partof a large-sized device. For example, a plurality of battery modules maybe connected with each other so as to construct a battery pack.

The unit cells may be secondary batteries that can be charged anddischarged. Typically, the unit cells may be nickel metal hydridesecondary batteries, lithium-ion secondary batteries, or lithium-ionpolymer secondary batteries. Among them, the lithium-ion secondarybatteries are preferably used because the lithium-ion secondarybatteries have high energy density and high discharge voltage. In termsof the shape of the unit cells, prismatic batteries or pouch-typebatteries are preferably used. More preferably, the pouch-shapedbatteries are used because the manufacturing costs of the pouch-shapedbatteries are low, and the weight of the pouch-shaped batteries small.

The unit cells may be stacked one on another without using additionalmembers so as to construct a battery module. Preferably, however, one ormore unit cells are mounted in a cartridge such that the outer surfacesof the unit cells are almost fully exposed to the outside, and aplurality of cartridges are stacked one on another to construct abattery module. Especially, when the pouch-shaped batteries, which havelow mechanical strength and in which the electrical connection betweenelectrode terminals of the batteries is difficult, are used as the unitcells, it is preferable that the pouch-shaped batteries be mounted inthe cartridge so as to construct a battery module.

The cartridge may have various different structures. In a preferredembodiment, the cartridge includes a pair of rectangular frame membersfor fixing the edges of the unit cells such that the upper and lowersurfaces of the unit cells are exposed to the outside when therectangular frame members are coupled with each other, one or moreplate-shaped unit cells are mounted between the frame members while theunit cells are arranged in the lateral direction, bus bars forconnecting electrode terminals of the unit cells are attached to upperend frames, and side frames of the cartridge have a height greater thanthat of upper and lower frames and the thickness of the unit cells whenthe unit cells are mounted in the cartridge.

The fundamental structure of the cartridge is nearly identical to thatof a cartridge disclosed in Korean Patent Application No. 2004-111699,which has been filed in the name of the applicant of the presentapplication. The disclosure of the above-mentioned Korean patentapplication is hereby incorporated by reference as if fully set forthherein.

When a plurality of cartridges, in which the unit cells are mounted, aresequentially stacked one on another to construct a battery module, andcontinuous flow channels are formed between the upper and lower endframes of the neighboring cartridges and between the upper and lowersurfaces of the unit cells facing each other. The gap defined betweenthe upper end frames of two neighboring cartridges constitutes a flowchannel inlet port.

According to the present invention, the flow channels defined betweenthe unit cells are at the predetermined angle to the flowing directionof the coolant at the flow channel inlet ports. As a result, thecartridge is constructed in a structure in which the side frames are atthe predetermined angle to the upper frames. Consequently, the coolantintroduced through the flow channel inlet ports of the upper end frames,which are disposed in the horizontal direction, flows through the flowchannels on the upper frames in the horizontal direction. When thecoolant flows through the flow channels defined between the unit cells,which are inclined at the same inclination angle as the side frames,however, the flow direction of the coolant is also inclined.

In a preferred embodiment, the lower end frame of each cartridge isinclined at the same angle as the upper frame of each cartridge.Consequently, it is possible to more easily accomplish the stackingprocess of the cartridges.

In accordance with another aspect of the present invention, there isprovided a medium- or large-sized battery pack including one or morebattery modules with the above-stated construction. The medium- orlarge-sized battery pack further includes a battery management system(BMS) for controlling the operation of the battery modules in additionto the battery modules.

The medium- or large-sized battery pack according to the presentinvention has high cooling efficiency. Consequently, the presentinvention is more preferably applied to a battery pack using lithiumsecondary batteries having a large amount of heat generation as unitcells. Although the size of the battery pack is small, the battery packaccording to the present invention provides high cooling efficiency.Consequently, the battery pack is preferably used as a compact powersource for electric vehicles, hybrid electric vehicles, or electricbicycles.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view illustrating a conventional batterycartridge;

FIG. 2 is a perspective view illustrating a battery module constructedby stacking a plurality of battery cartridges, one of which is shown inFIG. 1, one on another;

FIG. 3 is a typical view illustrating the flow of a coolant through aflow channel defined between the battery cartridges of the batterymodule shown in FIG. 2;

FIG. 4 is an enlarged view illustrating part A of FIG. 3;

FIG. 5 is a typical view illustrating a process for mounting unit cellsin a battery cartridge that can be used to construct a battery moduleaccording to a preferred embodiment of the present invention;

FIG. 6 is a perspective view illustrating the battery cartridge of FIG.5 having the unit cells mounted therein;

FIG. 7 is a side view typically illustrating inclined frame members ofthe battery cartridge shown in FIG. 6 and the unit cell mounted betweenthe inclined frame members;

FIG. 8 is a typical view illustrating a flow channel defined between thebattery cartridges of the battery module according to the preferredembodiment of the present invention and the flow of a coolant throughthe flow channel; and

FIG. 9 is an enlarged view illustrating part B of FIG. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be noted,however, that the scope of the present invention is not limited by theillustrated embodiments.

FIG. 5 is a typical view illustrating a process for mounting unit cellsin a battery cartridge that can be used to construct a battery moduleaccording to a preferred embodiment of the present invention, and FIG. 6is a perspective view typically illustrating the battery cartridge, inwhich the unit cells are mounted therein.

Referring to these drawings, a battery cartridge 400 is very similar oridentical in the basic structure to the battery cartridge 100 of FIG. 1.Specifically, a plurality of plate-shaped unit cells 201, 202, 203, 204are mounted between a pair of coupling type upper and lower framemembers 410 and 411 such that the unit cells are arranged in lateraldirection.

The unit cells 201, 202 . . . are pouch-shaped batteries. Electrodeterminals 211, 221, 212, 222 . . . protrude from the upper ends of theunit cells 201, 202 . . . . The electrode terminals 211, 221, 212, 222 .. . are electrically connected with the corresponding ones by bus bars(not shown) attached to either an upper end frame 420 of the upper framemember 410 or an upper end frame 421 of the lower frame member 411.

After the unit cells 201, 202 . . . are mounted between the upper framemember 410 and the lower frame member 411, the upper frame member 410and the lower frame member 411 are brought into tight contact with eachother, and then are coupled with each other. As a result, the upperframe member 410 and the lower frame member 411 have a symmetricalstructure. Consequently, the description of the structure of the upperframe member 410 is almost equally applied to the lower frame member411.

The upper frame member 410 is generally constructed in a rectangularstructure. The upper frame member 410 includes an upper frame 420, alower frame 440, and a plurality of side frames 430. The edges of theunit cells 201, 202 . . . are fixed by the contact regions of the upperand lower frame members 410 and 411, i.e., the upper end frames 420 and421, the side frames 430 and 432, and the lower end frames 440 and 441.In addition, the upper and lower surfaces of the unit cells 201 and 202are exposed to the outside through openings 450.

The side frames 430 and 431 are at a predetermined angle to the upperend frames 402 and 421, respectively, and the lower end frames 440 and441 are in parallel with the upper end frames 420 and 421, respectively.This structure is shown in more detail in FIG. 7. Referring to FIG. 7,the side frames 430 and 431 are at an angle of α to the upper end frames420 and 421, respectively. Consequently, electrode terminals 210 of theunit cell 200, which are coupled to the upper end frames 420 and 421,are in parallel with the upper end frames 420 and 421, like the upperend frames 420 and 421, whereas the cell body 230 of the unit cell 200is at the predetermined angle to the upper end frames 420 and 421, likethe side frames 430 and 431.

Referring back to FIGS. 5 and 6, the protruding height of the sideframes 430 and 431 is greater than that of the upper and lower endframes 420, 421, 430, and 431, and the protruding height of the sideframes 430 and 431 is greater than the thickness of the unit cells 201,202 . . . mounted between the side frames 430 and 431.

Consequently, when a plurality of cartridges 400 (see FIG. 6), in whichthe unit cells are mounted, are stacked one on another as shown in FIG.2, the cartridges are arranged such that the side frames are in contactwith each other, and therefore, gaps are defined along the upper endframes, the unit cells, and the lower end frames. The gaps constituteflow channels through which a coolant flows.

FIG. 8 is a typical view illustrating a flow channel defined between thebattery cartridges of the battery module according to the preferredembodiment of the present invention and the flow of a coolant throughthe flow channel.

Referring to FIG. 8, a flow channel 500 is formed between two cartridges401 and 402, which are stacked one on another. The flow channel 500 isslightly inclined by the above-described structure of the cartridges. Aflow channel inlet port 510 formed between the upper end frames 410 isdisposed in the horizontal direction, and the flow channel 500 formedbetween the unit cells 200 is at the predetermined angle to the flowchannel inlet port 510. Consequently, a coolant flows in the horizontaldirection while the coolant passes through the flow channel inlet port510. After the coolant is introduced into the flow channel 500, however,the coolant flows in an “S” shape as indicated by an arrow. When thecoolant is introduced into a flow channel outlet port 520 between thelower end frames 440, the coolant flows again in the horizontaldirection.

FIG. 9 is an enlarged view illustrating part B of FIG. 8.

Referring to FIG. 9, the S-shaped flow of the coolant through the flowchannel 500 describes a parabolic motion when viewing from a microscopicviewpoint. This is because the coolant introduced into the flow channelinlet port in the horizontal direction collides with the inclined unitcell 200. Consequently, the contact rate of the coolant to the unit cellis increased, and a large number of turbulent flows are created, whichprevents the occurrence of the velocity gradient as shown in FIG. 4. Asa result, the cooling efficiency of the unit cell 200 by the coolant isgreatly improved.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

As apparent from the above description, the contact rate of the coolantto the unit cells in the battery module according to the presentinvention is increased and a large number of turbulent flows are createdby the changing the flow channel through which the coolant flows.Consequently, the occurrence of the velocity gradient of the coolant inthe flow channel defined between the unit cells is prevented, andtherefore, the cooling efficiency of the battery module is improved.

Furthermore, a battery pack including the battery module has highcooling efficiency although the overall structure of the battery pack isnot greatly changed, or a large-sized cooling fan or a powerful drivingunit is not used. Consequently, the battery pack is preferably used as apower source for electric vehicles or hybrid electric vehicles.

1. A battery module, comprising: a plurality of unit cells stackedproximate to one another, the plurality of unit cells defining flowchannels therebetween, each unit cell of the plurality of unit cellsbeing longitudinally positioned at a first predetermined angle between 3and 15 degrees relative to a first wall of an input port for arespective flow channel, and each unit cell of the plurality of unitcells being further longitudinally positioned at a second predeterminedangle 3 and 15 degrees relative to a second wall of an outlet port forthe respective flow channel, the first and second walls being parallelto one another; and a cooling system that routes a coolant through theflow channels between the plurality of unit cells such that the coolantcontacts the plurality of unit cells to cool the plurality of unitcells.
 2. The battery module according to claim 1, wherein the coolantis air.
 3. The battery module according to claim 1, wherein the unitcells are lithium secondary batteries.
 4. The battery module accordingto claim 1, wherein the unit cells are pouch-shaped batteries.
 5. Amedium- or large-sized battery pack including one or more batterymodules according to claim
 1. 6. The battery pack according to claim 5,wherein the battery pack is used as a power source for electric vehiclesor hybrid electric vehicles.
 7. A battery module comprising: first andsecond frame members; a first unit cell disposed between the first andsecond frame members and supported by the first and second framemembers; third and fourth frame members, the third frame member beingdisposed on the second frame member; a second unit cell disposed betweenthe third and fourth frame members and supported by the third and fourthframe members; the first and second unit cells having a flow channeldefined therebetween, the first and second unit cells beinglongitudinally positioned at a first predetermined angle between 3 and15 degrees relative to an input port defined by the second and thirdframe members, and the first and second unit cells being furtherlongitudinally positioned at a second predetermined angle between 3 and15 degrees relative to an outlet port defined by the second and thirdframe members, the inlet port extending in a direction parallel to adirection in which the outlet port extends; and a cooling system thatroutes coolant through the input port and the flow channel such that thecoolant contacts the first and second unit cells to cool the first andsecond unit cells.
 8. The battery module according to claim 7, whereinthe coolant is air.
 9. The battery module according to claim 7, whereinthe unit cells are lithium secondary batteries.
 10. The battery moduleaccording to claim 7, wherein the unit cells are pouch-shaped batteries.11. The battery module according to claim 1, wherein bus bars forconnecting electrode terminals of the unit cells are attached to theframe member.
 12. A medium- or large-sized battery pack including one ormore battery modules according to claim
 8. 13. The battery packaccording to claim 12, wherein the battery pack is used as a powersource for electric vehicles or hybrid electric vehicles.